From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 69037 invoked by alias); 18 Apr 2019 15:48:46 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 36054 invoked by uid 89); 18 Apr 2019 15:48:24 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-25.4 required=5.0 tests=AWL,BAYES_00,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,KAM_SHORT,SPF_PASS autolearn=ham version=3.3.1 spammy= X-HELO: mx1.suse.de Received: from mx2.suse.de (HELO mx1.suse.de) (195.135.220.15) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 18 Apr 2019 15:48:06 +0000 Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id CB42FAFF5; Thu, 18 Apr 2019 15:48:03 +0000 (UTC) Subject: Re: [PATCH] Handle vfork in thread with follow-fork-mode child To: Pedro Alves , gdb-patches@sourceware.org References: <20190416150652.GA4805@delia> <3bb18786-b84d-ebdb-233a-92237f3c7764@redhat.com> From: Tom de Vries Message-ID: <4f660e6e-4592-a5aa-418e-bb47ab62c603@suse.de> Date: Thu, 18 Apr 2019 15:48:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <3bb18786-b84d-ebdb-233a-92237f3c7764@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2019-04/txt/msg00339.txt.bz2 On 18-04-19 11:12, Pedro Alves wrote: > On 4/18/19 9:02 AM, Tom de Vries wrote: >> On 17-04-19 19:45, Pedro Alves wrote: >> >>> + inf->vfork_parent = NULL; >> >> I was checking this and found dereferences of inf->vfork_parent after it >> was set to NULL here: >> ... >> else if (exec) >> { >> ... >> resume_parent = inf->vfork_parent->pid; >> ... >> and here: >> ... >> else >> { >> ... >> clone_program_space (pspace, inf->vfork_parent->pspace); >> ... >> >> To confirm, I did another testrun with aborts at the start of the >> blocks, and I found no regressions. So, either this is dead code, or we >> need test-cases that trigger these paths. > > Indeed, I noticed this yesterday, fixed it & wrote the extra testing, but > then had to leave for the day. Here is the updated patch with extra > testing, which involved moving the body of the testcases to a procedure, > and then testing with both "set detach-on-fork" "on" and "off". > > WDYT? > I've tested this both with native and native-gdbserver and found no regressions. I've also verified that both blocks mentioned above are triggered by the new test-cases. LGTM. Thanks, - Tom > From 575fecd185d07cd0d2f9d9aed5325e7b09b675e0 Mon Sep 17 00:00:00 2001 > From: Pedro Alves > Date: Thu, 18 Apr 2019 09:57:45 +0100 > Subject: [PATCH] [gdb] Handle vfork in thread with follow-fork-mode child > > When debugging any of the testcases added by this commit, which do a > vfork in a thread with "set follow-fork-mode child" + "set > detach-on-fork on", we run into this assertion: > > ... > src/gdb/nat/x86-linux-dregs.c:146: internal-error: \ > void x86_linux_update_debug_registers(lwp_info*): \ > Assertion `lwp_is_stopped (lwp)' failed. > ... > > The assert is caused by the following: the vfork-child exit or exec > event is handled by handle_vfork_child_exec_or_exit, which calls > target_detach to detach from the vfork parent. During target_detach > we call linux_nat_target::detach, which: > > #1 - stops all the threads > #2 - waits for all the threads to be stopped > #3 - detaches all the threads > > However, during the second step we run into this code in > stop_wait_callback: > > ... > /* If this is a vfork parent, bail out, it is not going to report > any SIGSTOP until the vfork is done with. */ > if (inf->vfork_child != NULL) > return 0; > ... > > and we don't wait for the threads to be stopped, which results in this > assert in x86_linux_update_debug_registers triggering during the third > step: > > ... > gdb_assert (lwp_is_stopped (lwp)); > ... > > The fix is to reset the vfork parent's vfork_child field before > calling target_detach in handle_vfork_child_exec_or_exit. There's > already similar code for the other paths handled by > handle_vfork_child_exec_or_exit, so this commit refactors the code a > bit so that all paths share the same code. > > The new tests cover both a vfork child exiting, and a vfork child > execing, since both cases would trigger the assertion. > > The new testcases also exercise following the vfork children with "set > detach-on-fork off", since it doesn't seem to be tested anywhere. > > Tested on x86_64-linux, using native and native-gdbserver. > > gdb/ChangeLog: > yyyy-mm-dd Tom de Vries > Pedro Alves > > PR gdb/24454 > * infrun.c (handle_vfork_child_exec_or_exit): Reset vfork parent's > vfork_child field before calling target_detach. > > gdb/testsuite/ChangeLog: > yyyy-mm-dd Tom de Vries > Pedro Alves > > PR gdb/24454 > * gdb.threads/vfork-follow-child-exec.c: New file. > * gdb.threads/vfork-follow-child-exec.exp: New file. > * gdb.threads/vfork-follow-child-exit.c: New file. > * gdb.threads/vfork-follow-child-exit.exp: New file. > --- > gdb/infrun.c | 31 +++++----- > .../gdb.threads/vfork-follow-child-exec.c | 66 ++++++++++++++++++++++ > .../gdb.threads/vfork-follow-child-exec.exp | 64 +++++++++++++++++++++ > .../gdb.threads/vfork-follow-child-exit.c | 52 +++++++++++++++++ > .../gdb.threads/vfork-follow-child-exit.exp | 60 ++++++++++++++++++++ > 5 files changed, 256 insertions(+), 17 deletions(-) > create mode 100644 gdb/testsuite/gdb.threads/vfork-follow-child-exec.c > create mode 100644 gdb/testsuite/gdb.threads/vfork-follow-child-exec.exp > create mode 100644 gdb/testsuite/gdb.threads/vfork-follow-child-exit.c > create mode 100644 gdb/testsuite/gdb.threads/vfork-follow-child-exit.exp > > diff --git a/gdb/infrun.c b/gdb/infrun.c > index 37713b24fee..37df561de0b 100644 > --- a/gdb/infrun.c > +++ b/gdb/infrun.c > @@ -915,10 +915,14 @@ handle_vfork_child_exec_or_exit (int exec) > int resume_parent = -1; > > /* This exec or exit marks the end of the shared memory region > - between the parent and the child. If the user wanted to > - detach from the parent, now is the time. */ > + between the parent and the child. Break the bonds. */ > + inferior *vfork_parent = inf->vfork_parent; > + inf->vfork_parent->vfork_child = NULL; > + inf->vfork_parent = NULL; > > - if (inf->vfork_parent->pending_detach) > + /* If the user wanted to detach from the parent, now is the > + time. */ > + if (vfork_parent->pending_detach) > { > struct thread_info *tp; > struct program_space *pspace; > @@ -926,7 +930,7 @@ handle_vfork_child_exec_or_exit (int exec) > > /* follow-fork child, detach-on-fork on. */ > > - inf->vfork_parent->pending_detach = 0; > + vfork_parent->pending_detach = 0; > > gdb::optional > maybe_restore_inferior; > @@ -941,7 +945,7 @@ handle_vfork_child_exec_or_exit (int exec) > maybe_restore_thread.emplace (); > > /* We're letting loose of the parent. */ > - tp = any_live_thread_of_inferior (inf->vfork_parent); > + tp = any_live_thread_of_inferior (vfork_parent); > switch_to_thread (tp); > > /* We're about to detach from the parent, which implicitly > @@ -964,7 +968,7 @@ handle_vfork_child_exec_or_exit (int exec) > if (print_inferior_events) > { > std::string pidstr > - = target_pid_to_str (ptid_t (inf->vfork_parent->pid)); > + = target_pid_to_str (ptid_t (vfork_parent->pid)); > > target_terminal::ours_for_output (); > > @@ -982,7 +986,7 @@ handle_vfork_child_exec_or_exit (int exec) > } > } > > - target_detach (inf->vfork_parent, 0); > + target_detach (vfork_parent, 0); > > /* Put it back. */ > inf->pspace = pspace; > @@ -997,10 +1001,7 @@ handle_vfork_child_exec_or_exit (int exec) > inf->removable = 1; > set_current_program_space (inf->pspace); > > - resume_parent = inf->vfork_parent->pid; > - > - /* Break the bonds. */ > - inf->vfork_parent->vfork_child = NULL; > + resume_parent = vfork_parent->pid; > } > else > { > @@ -1030,17 +1031,13 @@ handle_vfork_child_exec_or_exit (int exec) > set_current_program_space (pspace); > inf->removable = 1; > inf->symfile_flags = SYMFILE_NO_READ; > - clone_program_space (pspace, inf->vfork_parent->pspace); > + clone_program_space (pspace, vfork_parent->pspace); > inf->pspace = pspace; > inf->aspace = pspace->aspace; > > - resume_parent = inf->vfork_parent->pid; > - /* Break the bonds. */ > - inf->vfork_parent->vfork_child = NULL; > + resume_parent = vfork_parent->pid; > } > > - inf->vfork_parent = NULL; > - > gdb_assert (current_program_space == inf->pspace); > > if (non_stop && resume_parent != -1) > diff --git a/gdb/testsuite/gdb.threads/vfork-follow-child-exec.c b/gdb/testsuite/gdb.threads/vfork-follow-child-exec.c > new file mode 100644 > index 00000000000..80632d1772f > --- /dev/null > +++ b/gdb/testsuite/gdb.threads/vfork-follow-child-exec.c > @@ -0,0 +1,66 @@ > +/* This testcase is part of GDB, the GNU debugger. > + > + Copyright 2019 Free Software Foundation, Inc. > + > + This program is free software; you can redistribute it and/or modify > + it under the terms of the GNU General Public License as published by > + the Free Software Foundation; either version 3 of the License, or > + (at your option) any later version. > + > + This program is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + GNU General Public License for more details. > + > + You should have received a copy of the GNU General Public License > + along with this program. If not, see . */ > + > +#include > +#include > +#include > +#include > +#include > + > +static char *program_name; > + > +static void * > +f (void *arg) > +{ > + int res = vfork (); > + > + if (res == -1) > + { > + perror ("vfork"); > + return NULL; > + } > + else if (res == 0) > + { > + /* Child. */ > + execl (program_name, program_name, "1", NULL); > + perror ("exec"); > + abort (); > + } > + else > + { > + /* Parent. */ > + return NULL; > + } > +} > + > +int > +main (int argc, char **argv) > +{ > + pthread_t tid; > + > + if (argc > 1) > + { > + /* Getting here via execl. */ > + return 0; > + } > + > + program_name = argv[0]; > + > + pthread_create (&tid, NULL, f, NULL); > + pthread_join (tid, NULL); > + return 0; > +} > diff --git a/gdb/testsuite/gdb.threads/vfork-follow-child-exec.exp b/gdb/testsuite/gdb.threads/vfork-follow-child-exec.exp > new file mode 100644 > index 00000000000..5a28715fa0d > --- /dev/null > +++ b/gdb/testsuite/gdb.threads/vfork-follow-child-exec.exp > @@ -0,0 +1,64 @@ > +# Copyright (C) 2019 Free Software Foundation, Inc. > + > +# This program is free software; you can redistribute it and/or modify > +# it under the terms of the GNU General Public License as published by > +# the Free Software Foundation; either version 3 of the License, or > +# (at your option) any later version. > +# > +# This program is distributed in the hope that it will be useful, > +# but WITHOUT ANY WARRANTY; without even the implied warranty of > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > +# GNU General Public License for more details. > +# > +# You should have received a copy of the GNU General Public License > +# along with this program. If not, see . */ > + > +# Test following a vfork child that execs, when the vfork parent is a > +# threaded program, and it's a non-main thread that vforks. > + > +standard_testfile > + > +if {[build_executable "failed to prepare" $testfile $srcfile {debug pthreads}]} { > + return -1 > +} > + > +# DETACH indicates whether "set detach-on-fork" is enabled. It is > +# either "on" or "off". > + > +proc test_vfork {detach} { > + global binfile > + > + clean_restart $binfile > + > + if ![runto_main] then { > + fail "can't run to main" > + return 0 > + } > + > + delete_breakpoints > + > + gdb_test_no_output "set follow-fork-mode child" > + gdb_test_no_output "set detach-on-fork $detach" > + > + if {$detach == "off"} { > + gdb_test "continue" \ > + [multi_line \ > + "Attaching after .* vfork to child .*" \ > + ".*New inferior 2 .*" \ > + ".* is executing new program: .*" \ > + ".*Inferior 2 .* exited normally.*"] > + } else { > + gdb_test "continue" \ > + [multi_line \ > + "Attaching after .* vfork to child .*" \ > + ".*New inferior 2 .*" \ > + ".*Detaching vfork parent process .* after child exec.*" \ > + ".*Inferior 1 .* detached.*" \ > + ".*is executing new program: .*" \ > + ".*Inferior 2 .*exited normally.*"] > + } > +} > + > +foreach_with_prefix detach-on-fork {"off" "on"} { > + test_vfork ${detach-on-fork} > +} > diff --git a/gdb/testsuite/gdb.threads/vfork-follow-child-exit.c b/gdb/testsuite/gdb.threads/vfork-follow-child-exit.c > new file mode 100644 > index 00000000000..6ae254cce96 > --- /dev/null > +++ b/gdb/testsuite/gdb.threads/vfork-follow-child-exit.c > @@ -0,0 +1,52 @@ > +/* This testcase is part of GDB, the GNU debugger. > + > + Copyright 2019 Free Software Foundation, Inc. > + > + This program is free software; you can redistribute it and/or modify > + it under the terms of the GNU General Public License as published by > + the Free Software Foundation; either version 3 of the License, or > + (at your option) any later version. > + > + This program is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + GNU General Public License for more details. > + > + You should have received a copy of the GNU General Public License > + along with this program. If not, see . */ > + > +#include > +#include > +#include > + > +static void * > +f (void *arg) > +{ > + int res = vfork (); > + > + if (res == -1) > + { > + perror ("vfork"); > + return NULL; > + } > + else if (res == 0) > + { > + /* Child. */ > + _exit (0); > + } > + else > + { > + /* Parent. */ > + return NULL; > + } > +} > + > +int > +main (void) > +{ > + pthread_t tid; > + > + pthread_create (&tid, NULL, f, NULL); > + pthread_join (tid, NULL); > + return 0; > +} > diff --git a/gdb/testsuite/gdb.threads/vfork-follow-child-exit.exp b/gdb/testsuite/gdb.threads/vfork-follow-child-exit.exp > new file mode 100644 > index 00000000000..f07215d41c6 > --- /dev/null > +++ b/gdb/testsuite/gdb.threads/vfork-follow-child-exit.exp > @@ -0,0 +1,60 @@ > +# Copyright (C) 2019 Free Software Foundation, Inc. > + > +# This program is free software; you can redistribute it and/or modify > +# it under the terms of the GNU General Public License as published by > +# the Free Software Foundation; either version 3 of the License, or > +# (at your option) any later version. > +# > +# This program is distributed in the hope that it will be useful, > +# but WITHOUT ANY WARRANTY; without even the implied warranty of > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > +# GNU General Public License for more details. > +# > +# You should have received a copy of the GNU General Public License > +# along with this program. If not, see . */ > + > +# Test following a vfork child that exits, when the vfork parent is a > +# threaded program, and it's a non-main thread that vforks. > + > +standard_testfile > + > +if {[build_executable "failed to prepare" $testfile $srcfile {debug pthreads}]} { > + return -1 > +} > + > +# DETACH indicates whether "set detach-on-fork" is enabled. It is > +# either "on" or "off". > + > +proc test_vfork {detach} { > + global binfile > + > + clean_restart $binfile > + > + if ![runto_main] then { > + fail "can't run to main" > + return 0 > + } > + > + gdb_test_no_output "set follow-fork-mode child" > + gdb_test_no_output "set detach-on-fork $detach" > + > + if {$detach == "off"} { > + gdb_test "continue" \ > + [multi_line \ > + "Attaching after .* vfork to child .*" \ > + ".*New inferior 2 .*" \ > + ".*Inferior 2 .*exited normally.*"] > + } else { > + gdb_test "continue" \ > + [multi_line \ > + "Attaching after .* vfork to child .*" \ > + ".*New inferior 2 .*" \ > + ".*Detaching vfork parent process .* after child exit.*" \ > + ".*Inferior 1 .* detached.*" \ > + ".*Inferior 2 .*exited normally.*"] > + } > +} > + > +foreach_with_prefix detach-on-fork {"off" "on"} { > + test_vfork ${detach-on-fork} > +} >